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IFN around M95 & M96?


gorann

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Hmmm.  I'd be interested to know what issues using darks that don't exactly match the duration of your lights might throw up...

Anyway, have you changed your image train since shooting the lights?  It may be possible to shoot some flats now and see if there is anything that could be causing the effects in your image.

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I stretched the living daylights out of the tiffs you provided, and this is what I came up with

1932304739_M9596halfstack0203-0331.thumb.jpg.deb9b65b78f35fb27b3aac1a6dbb8f30.jpg

1244289942_M95-96halfstack0333-0459.thumb.jpg.83e5214d0a62582898862d00f49862af.jpg

Process: 

  • crop to remove any stacking artefacts
  • DBE with the minimum number of samples to get rid of vignetting. Sample size 35, one sample in each corner, one sample on each edge, one sample in the middle, and one sample midway from each corner to the centre. No samples anywhere near a galaxy or larger star.
  • Layer 1 removed (1 pixel information) to reduce the noise
  • Histogram stretch
  • MS HDR compression to get some details in the galaxies, to keep the image pleasing)
  • Further stretch
  • resample 50%
  • saved as jpeg

I think that the dark patch immediately next to M95 (?, right) is a dust bunny, as is the dark circular pattern midway but somewhat lower than the galaxies. The slightly brighter area below and to the left of M96 (left) may be a real dust cloud.

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30 minutes ago, wimvb said:

I stretched the living daylights out of the tiffs you provided, and this is what I came up with

1932304739_M9596halfstack0203-0331.thumb.jpg.deb9b65b78f35fb27b3aac1a6dbb8f30.jpg

1244289942_M95-96halfstack0333-0459.thumb.jpg.83e5214d0a62582898862d00f49862af.jpg

Process: 

  • crop to remove any stacking artefacts
  • DBE with the minimum number of samples to get rid of vignetting. Sample size 35, one sample in each corner, one sample on each edge, one sample in the middle, and one sample midway from each corner to the centre. No samples anywhere near a galaxy or larger star.
  • Layer 1 removed (1 pixel information) to reduce the noise
  • Histogram stretch
  • MS HDR compression to get some details in the galaxies, to keep the image pleasing)
  • Further stretch
  • resample 50%
  • saved as jpeg

I think that the dark patch immediately next to M95 (?, right) is a dust bunny, as is the dark circular pattern midway but somewhat lower than the galaxies. The slightly brighter area below and to the left of M96 (left) may be a real dust cloud.

Have a look at these images I found on Astrobin. Give the second one a stretch. The dark area around M95 could be real and the second one show also other similar structures.

https://www.astrobin.com/82910/B/

https://www.astrobin.com/74530/

 

 

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1 hour ago, x6gas said:

Hmmm.  I'd be interested to know what issues using darks that don't exactly match the duration of your lights might throw up...

Anyway, have you changed your image train since shooting the lights?  It may be possible to shoot some flats now and see if there is anything that could be causing the effects in your image.

All taken apart unfortunately, so no flats. I will do a stack of the lights without master dark.

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13 minutes ago, gorann said:

Have a look at these images I found on Astrobin. Give the second one a stretch. The dark area around M95 could be real and the second one show also other similar structures.

https://www.astrobin.com/82910/B/

https://www.astrobin.com/74530/

 

 

The first image is suspicious. What would the physical reason be for a hole in ifn just where a galaxy is situated, and that hole being symmetrical as well? The second image does show some background variation, but I can't completely match it with the background in your image.

If you want to pursue this, this reference will come in handy.

http://www.aicccd.com/archive/aic2005/The_unexplored_nebula_project-smandel.pdf

There is no reason to assume that IFN is only limited to the polar region around M81 and Polaris. But the reference pdf shows that IFN varies a lot in intensity across the sky globe. That is probably why it has not been picked up regularly before other than near Ursa Major.

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I would say that this is genuine stuff, pity that full calibration is missing from the workflow, it would be much easier to tell.

Interesting thing is that there is different level of vignetting between first and second stack - but I think that it can be explained by missing flats. Doing normalization of frames when not fully calibrated will do that sort of thing.

2 hours ago, wimvb said:

I stretched the living daylights out of the tiffs you provided, and this is what I came up with

1932304739_M9596halfstack0203-0331.thumb.jpg.deb9b65b78f35fb27b3aac1a6dbb8f30.jpg

1244289942_M95-96halfstack0333-0459.thumb.jpg.83e5214d0a62582898862d00f49862af.jpg

Process: 

  • crop to remove any stacking artefacts
  • DBE with the minimum number of samples to get rid of vignetting. Sample size 35, one sample in each corner, one sample on each edge, one sample in the middle, and one sample midway from each corner to the centre. No samples anywhere near a galaxy or larger star.
  • Layer 1 removed (1 pixel information) to reduce the noise
  • Histogram stretch
  • MS HDR compression to get some details in the galaxies, to keep the image pleasing)
  • Further stretch
  • resample 50%
  • saved as jpeg

I think that the dark patch immediately next to M95 (?, right) is a dust bunny, as is the dark circular pattern midway but somewhat lower than the galaxies. The slightly brighter area below and to the left of M96 (left) may be a real dust cloud.

I think this processing shows effect well, and to my eye it's there in both images - so we can conclude that it's not due to clouds.

It does not look like it's due to dust shadows either - I'm not seeing indications of that in image.

Out of interest, I see many people posting raw linear stack in 16 bit format, is this default thing for PI (and DSS for that matter)?

Do people actually work with only 16bit precision when processing their images?

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2 hours ago, vlaiv said:

I would say that this is genuine stuff, pity that full calibration is missing from the workflow, it would be much easier to tell.

Interesting thing is that there is different level of vignetting between first and second stack - but I think that it can be explained by missing flats. Doing normalization of frames when not fully calibrated will do that sort of thing.

I think this processing shows effect well, and to my eye it's there in both images - so we can conclude that it's not due to clouds.

It does not look like it's due to dust shadows either - I'm not seeing indications of that in image.

Out of interest, I see many people posting raw linear stack in 16 bit format, is this default thing for PI (and DSS for that matter)?

Do people actually work with only 16bit precision when processing their images?

Nice if it is real! I just have to revisit it. 16 bit is what I need for PS. At least PS CS5 that I use only works partially in 32 bit.

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1 hour ago, ollypenrice said:

Dropbox not playing for me at the moment. Will try later!

Olly

No problem Olly,

meanwhile I keep the background at a level I can trust. Here it is with the RGB data - I don't think it needs flats as long as I don't I venture into IFN territory:

20190212_M95_M96_RGB_PS50smallSign.jpg

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